Orthopaedic surgeons have the option of utilizing computer-assisted navigation systems to provide intraoperative surgical guidance. For example, computer navigation can provide data on functional parameters such as leg length and offset changes during hip arthroplasty. The purported benefits of computer navigation include reduction of outliers and adverse outcomes related to intraoperative positioning of surgical hardware.
Despite obvious clinical benefit, these systems have had limited adoption due to their expense, the learning curve and training requirements for surgeons and, for some systems, the additional procedure and time associated with hardware insertion into the patient. Surgeons that do not use these systems are limited to traditional techniques that are generally based on visual analysis and surgeon experience. However, these techniques are inconsistent, often leading to outliers in functional parameters which may affect patient satisfaction and implant longevity.
Details of one such technique, specifically used in a minimally invasive hip arthroplasty technique referred to as the direct anterior approach, are mentioned in the description of a total hip arthroplasty surgery, by Matta et al. in “Single-incision Anterior Approach for Total hip Arthroplasty on an Orthopaedic Table”, Clinical Ortho. And Related Res. 441, pp. 115-124 (2005). The intra-operative technique described by Matta et al. is time-consuming and has a high risk of inaccuracy due to differences in rotation, magnification and/or scaling of various images, because the technique relies upon acquiring a preoperative and intraoperative image that are scaled and positioned equivalently. The technique also requires consistent patient positioning in the preoperative and intraoperative images, including positioning of the femur relative to the pelvis. Maintaining femoral position while performing hip arthroplasty can pose a significant and often unrealistic challenge to a surgeon that is focused on performing a procedure. The high risk of inaccurate interpretation using this technique has limited its utility in guiding surgical decision making.
What appears to be a software implementation of this technique is described by Penenberg et al. in U.S. Patent Publication No. 2014/0378828, which is a continuation-in-part application of U.S. Pat. No. 8,831,324 by Penenberg. While the use of a computer system may facilitate some aspects of this technique, the underlying challenges to the technique are consistent with the challenges to Matta's approach, and limit the system's potential utility.
The challenge of accounting for differences in femoral positioning, ever-present in existing non-invasive guidance technologies for hip arthroplasty, could be solved by developing a system and method that corrects for deviations between preoperative and intraoperative femoral positioning.
It is therefore desirable to have a non-invasive system and method that provides intraoperative guidance and data by correcting for deviations in femoral positioning between preoperative and intraoperative images.